The present invention relates to the technical field of pulsed, high-power electrical generators and in particular to high-voltage spark gap devices operating in conjunction with such generators.
Using spark gap devices with high-power electrical generators, a set of specific criteria is involved, among which foremost that of their inductance which must be low in order to attain the shortest discharge times.
A number of designs already have been proposed in this field.
The monogap spark device is a gas spark-gap device consisting of two mutually opposite main electrodes. The trigger electrode is configured between the two main ones and when a high-amplitude pulse is applied to this trigger electrode, it will create electrical paths in the gases at regular time intervals under optimal conditions.
This spark gap device entails the drawback that its inherent geometry precludes low inductances despite the formation of several electrical paths. Illustratively a spark gap device of this design entails a minimum inductance of about 20 nh.
Another spark gap device design already has been proposed. This is the surface spark gap. It operates substantially on the same principle as the above described single gap spark gap devices, except that the current paths follow the surface of a dielectric and hence are situated closer to the current-loop closing means. Even if the latter entail a low and admissible inductance of about 5 nh, they still may not be used for the high voltages that are fed from the high-voltage generators in conjunction with which the spark gap devices must operate. The main difficulty is to adjust the triggering system within the spark gap devicexe2x80x94when it can be done at all.
Lastly a third known spark gap device is the multiple spark gap device of low inductance wherein the charge voltage is spread across several gaps. In this design, a main electrode receives a voltage pulse and enables the closing of the gaps by capacitive coupling.
While the performance of this spark-gap device is fairly satisfactory and it matches high-voltage generators, it does nevertheless incur some drawbacks. In the first place a simple change in the geometry of this spark gap device mandatorily entails making a new mold. As a result additional costs are caused by cold moldingxe2x80x94which is an elaborate and uncertain procedure as noted by the high number of malfunctions of several series of spark gap devices of this kind. Also, to attain optimal operation, the trigger electrode must be molded into a dielectric structure between the current paths and the current-loop closing means. This feature is near mandatory and precludes moving the current paths and the current-loop closing means nearer each other in order to lower the spark gap device""s inductance. Another drawback is that the inductance of this spark gap device still is excessive and as a result research into the electric arcs from the path generating main electrodes shows that not all the paths are initiated: when a first path is formed, the voltage at the spark gap device terminals drops and may affect the closure of the other paths. Accordingly the observed inductance of about 10 to 15 nh of this spark gap device is too high to assure proper spark gap device operation when a high voltage is applied to it.
The objective of the present invention is to remedy the above described drawbacks by proposing a high-voltage spark gap device allowing substantial reduction of its inductance so as to attain triggering all arcing paths at each discharge, and to do so at very high voltages.
Another objective of the present invention is to create a reliable spark gap device making possible a mechanical design circumventing molding the spark-gap device case and thus allowing flexibility when determining operational parameters such as gap size and number of arcing paths.
Lastly the purpose of the invention is improving high-power electric generator performance while reducing manufacturing costs by means of some product independence from the manufacturing process.
Accordingly the objective of the present invention is a spark gap device for a high-power electric generator, namely a high-voltage spark gap device comprising an electric trigger system, furthermore two mutually spaced main electrodes in particular spheres, which operate pairwise and which are mutually oppositely situated, and current-loop closing means that are separated by a dielectric from the main electrodes, said spark gap device being characterized in that the electric trigger system is fitted with as many trigger electrodes as there are main electrodes in the spark-gap device, said trigger electrodes being fitted with a protective insulator and each being received in a different spark-gap device main electrode.
Preferably the spark-gap device main electrodes are kept on the dielectric by means of slides.
The main electrodes are able to slide within these slides and can be individually pressed against the dielectric by means such as springs.
In a preferred embodiment of the invention, the spark gap device is a high-voltage, multigap device operating in air at ambient or higher pressure, the gaps between the main electrodes being controlled by spacers.
The dielectric used in the spark gap device which is the object of the present invention consists of thin insulating layers. Moreover the protective insulator of the trigger electrodes may be implemented by a high-voltage cable.
The invention offers the advantage of a high-voltage spark gap device of a design much simpler than those of the extant spark gap devices. As a result such spark gap devices of the invention are more economical.
Another advantage of the present invention is the improvement in performance of the spark gap devices cooperating with high-power generators on account of reducing the spark-gap device inductance and thereby enabling closing all paths at each firing.